Manufacture of abrasive articles



Jgn. 23, 1934. KlRcHNE Mmumdwunflor ABRAYSIVE ARTICLES Filed Nov. 4,1931 T, J I

INVENTOR 1. w v HENRY V mam-mu.

ATTORN EY Patented Jan. 23, 1934 1,944,184 MANUFACTURE or anassrvaARTICLES Henry P. Kirchner, Niagara Falls, N. Y., assignor to TheCarborundum Company, Niagara Falls, N. Y., a corporation of PennsylvaniaApplication November 4, 1931. Serial No. 578,004

' 8 Claims. (or 51-201) This invention relates to improvements in themanufacture of abrasive articles and is applicable to abrasive wheelsintended for peripheral grinding, although not limited to this method ofgrinding.

A typical operation in which abrasive wheels are subjected totemperature changes is that-of grinding wood to produce paper pulp.Wheels intended for this type of service must resist tem- The use ofthese crusher leads is familiar particularly to the gun and ammunitionart for measuring breach pressure. My invention is not devoted to newmethods for measuring definite flange pressures, but has t'o'dowith themaintaining at a constant value any derived or predetermined flangepressure when the assembly is subjected to temperature change.

A large abrasive wheel, such as is used for- 10. perature changes atleast from minus 40 degrees pulp grinding, is made almost invariablyof,mate-'- centigrade to plus 100 degrees centigrade. They furthermoremust be made very rugged mechanically, in order to perform under loadsas high as 2000 horse power. They are made in sizes as heavy as eighttons, requiring a sixteen inch diameter steel spindle, and are mountedbetween right and left-hand threaded flanges to guarantee their propermechanical functioning and safety. I

The serious difliculty encountered in the operation of an artificialabrasive wheel for such purposes is the building up of excessive flangepres-- sure which may lead to the destruction of the wheel. Thesepressures may also exist in the mounted natural sandstone assemblies.

The more important causes of flange pressure are due (1) to the largedriving torque, and (2) to the action of differential expansion betweensteel spindle and abrasive body when assemblies are subjected totemperature changes. The pressure due to the first cause may amount tofrom 500 to 900 pounds per square inch under the flanges and is notserious, but is, in fact, essential in order th is the wheel may performits work. The. incre e in pressure due to temperature change, such ascooling the wheel from 100 degrees centigrade to 10 degrees centigrade,however, may amount to three or four thousand pounds per square inch,and it isthe magnitude of these secondary pressures acting upon theabrasive that, to a large degree, causes cracking of such wheels.

The status of the prior art is such that constant flange pressure is anideal but unrealized condition for assemblies which may be subjected totemperature changes. It would be still more advantageous to be able toimpose a predetermined, definite, flange pressure, especially for thelarger sizes of abrasive wheels which require heavy power input, buthere again the inability to maintain the pressure constant has preventedproper development of this phase of the problem. There are variousmechanical methods which may be used to measure pressure and place adefinite flange pressure upon an abrasive wheel such as small hydraulicpistons and suitable gauges placed between the flanges, or flangepressures may be determined by measuring the distortion of crusher'leadssuitably embedded in the flanges under a definite area of flangebearing.

rial that has a lower coefllcient of thermal expansion than the steelshaft upon which it is mounted. The flanges that grip the sides of thewheel are threaded in left and right-hand directions, respectively, sothat the power that turns the shaft tightens the flange grip upon thewheel sufliciently to carry the required load. The wheel and shaftbecome very hot during use and, consequently, the shaft lengthens morethan the abrasive body. During this change, however, the power continuesto take up this increase in shaft 'length and preserves the tight flangegrip upon -mal length when cool. The abrasive cannot contractsufllciently to afford the necessary relief. Consequently high pressuresupon the abrasive result. If an abrasive wheel is capable of resistingthe first few cycles of heating and cooling (possibly as a result of aslight disintegration of the cement grouting material such as iscommonly used under the driving flanges), the repeated cycles ofoperation cause the same extra tightening of the flanges, and coolingreapplies the same heavy flange pressure with its attendant threat uponthe physical integrity of the wheel. The are two broad classificationsinto which assembly methods for these large wheels fall; viz. (1) thosewhich provide a ribbed metallic hub or drum structure wherein therotating forces are applied to the abrasive entirely by means of largeribs which are inserted into the abrasive, 'said ribs being parallel tothe driving shaft and contacting with the abrasive essentiallythroughout the length of the arbor hole, and (2) those which provide nohub in the arbor hole, but which drive the wheel entirely by pressuredirected upon the wheel by the flanges. My invention has to do .chieflywith this latter type of mounting but also applies to certain modifieddesigns of the former class, and provides means for preventing any de-Fvelopment of excess flange pressure by permitting freedom oflongitudinal movement of the more hlgly expansive member (usually thesteel driving shaft) while still pressing the necessary flange pressureagainst the abrasive member by means of tie bolts which are made topossess the same expansion coeflicient as the abrasive member.

The invention is illustrated by the accompanying drawing in which:

Figure 1 is an axial section of an abrasive whee and its drivingflanges;

Figure 2 is an end view of the wheel shown in Fi 1;

Figure 3 is an axial section of a reinforced seg-- mental abrasive wheeland its driving flanges; and

Figure 4 is an end view of the wheel shown in Fi 3.

A typical manner in which my invention may be carried out is shown inFigures 1 and 2, where an abrasive annulus 1 is held between flanges 3and 4 which in turn are mounted upon a driving spindle or shaft 2.Flange 3 is threaded upon shaft 2 by threads 9 and locked firmly inposition by lock nuts 7 and 8. Flange 4 is slidably mounted upon shaft 2and is made rotatable by means of key 10 which is supported firmly inshaft 2 but is slidably connected with flange 4. Bolts 5 are passedthrough flanges 3 and 4, and tightening the nuts 6 causes the flanges togrip the abrasive annulus firmly enough to transmit power to the wheeland answer the requirements for operating the wheel. The degree to whichthe tightening is carried should not be excessive, and is easilyattained by the use of ordinary judgment of those skilled in the art ofassembling and using such abrasive wheels.

If the assembly in hand does require a definite amount of pressure to beimposed by the flanges, then methods such as referred to above are usedto attain this end.

The bolts 5 are composed of a material possessingsubstantially the samecoefficient of thermal expansion as the abrasive annulus 1. It will beseen, therefore, that no stresses due to differential contraction can bebuilt up between the annulus 1 and the shaft 2 because the more highlyexpansive member, namely the shaft 2, is freeto elongate or sh'orten bysliding through one flange. It will be seen that, if the shaft were notthus free to shorten, serious pressures would be transmitted to theabrasive annulus 1 by means of the clamping members 3 and 4. One

v class of materials satisfactory for the tie rods 5 is the group ofnickel steel alloys containing from 30 to 42 per cent of nickel. Thecoefficients of thermal expansion of artificial abrasives range from 3 x10- per centigrade degree to '7 x 10" per centigrade degree and thecoeflicients of thermal expansion obtainable by selecting definitecompositions in the class of steels cited range from 1 x 10- to 12 x 10-per centigrade degree; hence, there is no diiflculty in obtaining anickel steel alloy to match with sufficient accuracy the thermalcharacteristics of any abrasive selected for use.

As specific examples showing that a certain composition of steelpossesses a coeflicient of expansion substantially the same as that ofan artificial abrasive, I will tabulate data from results which haveactually been determined and used.

It should also be made clear that my invention is fully operative tomaintain flange pressure constant during variations of temperature andoperating conditions regardless of the relative difference in expansioncoeflicients between the abrasive and the spindle; that is, it makes nodifference how much the expansion of the spindle is greater or less thanthat of the abrasive member between the flanges, inasmuch as the use ofmy slidably mounted flange in conjunction with the bolts which are ofthe same thermal expansion as the abrasive takes care of all suchdifferences.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is embodied in the following claims.

, I claim:

1. As an article of manufacture, an abrasive wheel adapted forperipheral grinding wherein the power is transmitted from opposeddriving flanges which are pressed axially against the abrasive wheel bymeans of bolts and nuts threaded on said bolts, one of said flangesbeing slidable on the driving shaft and the'bolts having approximatelythe same coeflicient of expansion as the abrasive whereby stresses dueto thermal change are prevented from accumulating. 4

2. As an article of manufacture, an abrasive wheel adapted forperipheral grinding and driving means for said wheel comprising a shaft,a pair of oppositely disposed driving flanges-drivingly connected tosaid shaft and each adapted to transmit torque from flange to wheel bysimple frictional engagement, one of said flanges being free to slide onthe driving shaft while not rotatable with respect to said drivingshaft, and manu- 13 ally operated means for adjusting the axial pressurebetween the flanges and the abrasive wheel.

3. As an article of manufacture, an abrasive wheel adapted forperipheral grinding and driving means for said wheel comprising a shaft,a 1 pair of oppositely disposed driving flanges drive ingly connected tosaid shaft and each adapted to transmit torque from flange to wheel bysimple frictional engagement, one at' least of said flanges being freeto slide on the driving shaft, and means 1 for adjusting the axialpressure between then. flanges and wheel, said means comprising aplurality of tie rods possessing substantially the same coeflicient ofexpansion as the abrasive article and means on the tie rods for manualadjustment 3 of the tension exerted by the rods on flanges and wheel.

4'. As an article of manufacture, an abrasive wheel adapted forperipheral grinding which consists of adriving spindle, an abrasiveannulus 1 surrounding the spindle, two flanges adapted to fit againstthe abrasive annulus and mounted upon the spindle, one of said flangesbeing threaded and looked upon the spindle and the other flange beingslidable on but rotatable with the spindle, and rods of a metalpossessing substantiallythe same coefficient of thermal expansion as theabrasive annulus and provided with clamping means to hold the twoflanges tightly 4 against the abrasive annulus.

5. A method of mounting an abrasive wheel adapted for peripheralgrinding which comprises mounting said wheel upon a spindle betweendriving flanges, fastening one of said flanges rigidly to the drivingshaft, slidably mounting the other of said driving flanges on'thedriving shaft to turn therewith, and clamping the two flanges againstthe abrasive 'wheel by means of clamps which have substantially the samecoeflicient of expans onaa the abrasive wheel.

6. A method of mounting a reinforced segmental abrasive wheel adaptedfor peripheral grinding which comprises mounting said wheel upon aspindle between flanges, fastening one of said flanges rigidly to thedriving shaft in adjustable position, slidably mounting the other ofsaid driving flanges on the driving shaft to turn therewith, andclamping the two flanges against the abrasive wheel by means of clampswhich have substantially the same coefficient of expansion as theabrasive wheel whereby stresses due to thermal changes are preventedfrom accumulating.

7. A method of mounting an abrasive wheel to withstand temperaturechanges of the order of magnitude of one hundred oentigrade degrees,

which method comprises mounting the wheel between driving flanges whichare pressed against the wheel by means of clamps having the samecoeflicient of expansion as the abrasive, fastening one of the drivingflanges rigidly to the driving shaft in adjustable position, andslidably mounting the other of the driving flanges on the driving shaftby means which compel the lastmentioned flange to turn with the drivingshaft.

8. The method of mounting a segmental abrasive wheel which comprisesclamping the segments between terminal driving flanges by means of metalrods having substantially the same coeflicient of expansion as theabrasive, clamping one of the driving flanges to a shaft in adjustableposition, and providing the other flange with a sliding connection withthe shaft, which connection compels the last-mentioned flange to rotatewith the shaft.

HENRY P. KIRCHNER.

